During the operation of an engine, in order to reduce NOx emissions, a portion of exhaust gas is led into the air intake pipe, and mixed with fresh air or atomized gas mixture before entering the engine cylinders to undergo combustion—this is known as exhaust gas recirculation. However, if too much exhaust gas takes part in recirculation, the engine's performance will be affected. Therefore the rate of exhaust gas recirculation should be controlled, so as to lower the content of pollutants emitted by the vehicle without lowering the engine's performance.
An exhaust gas recirculation valve is generally used to regulate the exhaust gas recirculation rate. Specifically, the degree of opening of the exhaust gas recirculation valve is controlled according to the operating conditions of the engine, in order to regulate the exhaust gas recirculation rate. For example, when the engine is idling or under full load, the exhaust gas recirculation valve is closed; when the engine is under a partial load, the exhaust gas recirculation valve is opened.
The exhaust gas recirculation valve generally includes a sealing system, to prevent exhaust gas and carbon deposits from entering the valve body interior. Ingress of exhaust gas into the valve body interior will cause corrosion of internal valve members, thereby shortening the life of the exhaust gas recirculation valve. Accumulation of carbon deposits on the valve stem will cause increased resistance to movement of the valve stem or even seizure thereof.
Existing exhaust gas recirculation valve sealing systems generally only include one set of sealing elements, but this is unlikely to completely prevent exhaust gas leakage. Moreover, carbon deposits are likely to stick to the valve stem or even enter the valve body interior; as a result, valve life is reduced and valve reliability cannot be guaranteed.